Mancini's future with the reigning Premier League champions has been questioned and Saturday's 2-0 defeat at Everton has increased rumours over his situation.
Despite trailing leaders Manchester United in the table by 15 points, Platt has said that Mancini will not be affected by the rumours over his future.
"There is an appreciation of Roberto from the supporters and the owners," Platt told Sky Sports News.
"The expectancy levels of Roberto Mancini are a lot higher than what people think. If people want to talk about rumours and negatives that is up to them. We can't stop that.
"If people want to do things like that, they can. All I know is that during his career he has won things. That is what his focus, desire and intensity is about. He won't want stop wanting to win things."
City face Newcastle United on March 30.